1. Field of the Invention
This invention relates to methods and systems for the communication of telephone and modem signals over AC power lines. More specifically, the invention relates to the use of the digital techniques of differential binary phase shift keying modulation techniques in AC power line communications.
2. Description of Related Art
A variety of telephone and modem communications systems which take advantage of the AC power line for communications within a building or facility are well known in the art. Generally, these prior systems use analog frequency modulation techniques and fail to take advantage of digital processing and modulation techniques.
The reader is referred to the following U.S. patent documents for general background material. Each of these patents is hereby incorporated by reference in its entirety for the material contained therein.
U.S. Pat. No. 4,562,415 describes an apparatus and method, which provides PSK modulation utilizing a single balance mixer.
U.S. Pat. No. 4,829,543 describes a method and apparatus for phase-coherently demodulating a multipath-impaired time division multiple access QPSK data timeslot.
U.S. Pat. No. 5,025,452 describes a spread spectrum communications system that provides full-duplex voice/data radio communications with a single specified FCC ISM band.
U.S. Pat. No. 5,068,890 describes a combined telephone and electric power distribution system, wherein the signal conducting means and electric power conducting means are routed along-side each other to/from various utilization points.
U.S. Pat. No. 5,319,634 describes a method and system for conducting multiple access simultaneous telephone communications in full duplex either over the power lines of a building or using RF transmission.
U.S. Pat. No. 5,353,301 describes a method and apparatus for combining. multipath spread-spectrum signals, that is accomplished by detecting an envelope of an input differential phase shift keyed signal communicated over a communication channel.
U.S. Pat. No. 5,422,913 describes a high frequency transmitter that comprises a large number of narrow band channels spaced over a broad bandwidth transmission, using differential phase shift key modulations.
U.S. Pat. No. 5,488,629 describes a signal processing circuit that is provided with a frequency conversion circuit for converting a spread quadrature modulation signal of a carrier band into a baseband signal, a first correlator, a second correlator, a third correlator, a forth correlator spreading code, a decoding circuit, a first and second multiplier, a first and second adder, a judgment circuit, and a subtractor.
U.S. Pat. No. 5,499,272 describes a digital communications receiver that provides joint MLSE equalization and diversity combining.
U.S. Pat. No. 5,504,777 describes a communications system programmable to operate at a selected one of multiple frequency ranges and any one of a plurality of modulation schemes and data rights including an open architectural bus line for linking a plurality of board level units.
U.S. Pat. Nos. 5,528,585 and 5,546,383 describe a power-conserving time division multiple access (TDMA) radio telephone system, in which a cluster of subscriber stations, remote from a base station, employ a common pool of frequency-agile modems, each of which digitally synthesizes, on a timeslot-by-timeslot basis, the different channel-identifying intermediate frequencies needed to support communications between several of the subscriber stations and the base station.
U.S. Pat. No. 5,546,422 describes an acknowledgement paging system, which fits within the existing infrastructure of a paging network and which provides low cost manufacture and low power operation while still enabling the acknowledgement paging over long distances.
U.S. Pat. No. 5,579,304 describes a code-division multiple-access receiver that carries out the following steps whenever it recognizes a symbol boundary in the received baseband signal: first it estimates the value of the symbol; next it estimates an interference signal and modifies the baseband signal. These steps are iterated for each symbol.
U.S. Pat. No. 5,592,506 describes a method for demodulating a received spread-spectrum signal using a minimum-shift-keyed (MSK) receiver.
U.S. Pat. No. 5,610,939 describes a digital correlator used in a receiving component of a spread spectrum communication system of a direct sequence modulation type.
U.S. Pat. No. 5,640,333 describes a communications system that is programmable to operate at a selected one of multiple frequency ranges and any one of a plurality of modulation schemes and data rights including an open architectural bus line for linking a plurality of board level units.
U.S. Pat. No. 5,661,802 describes a telephone auxiliary power distribution system in a building has a flexible multi-conductor signal and power distribution cable; which cable originates from a central signal and power management facility located near the point where the telephone utility line enters the building and extends from there to each of numerous locations within the building.
U.S. Pat. No. 5,689,527 describes a communications system programmable to operate at a selected one of multiple frequency ranges and any one of a plurality of modulations schemes and data rights including an open architectural bus line for linking a plurality of board level units.
U.S. Pat. No. 5,706,313 describes a decoding apparatus that decodes a coherent, differentially encoded multi-level phase shift keying (DEPSK) modulated signal.
U.S. Pat. No. 5,706,428 describes a wireless LAN includes first stations adapted to operate at a 1 or 2 Mbps data rate and second stations adapted to operate at 1, 2, 5 or 8 Mbps data rate.
U.S. Pat. No. 5,712,872 describes a communications system that is programmable to operate at a selected one of multiple frequency ranges and any one of a plurality of modulations schemes and data rights, that includes an open architectural bus line for linking a plurality of board level units.
U.S. Pat. No. 5,729,571 describes a non-coherent digital receiver of a spread spectrum communication system for baseband synchronizing of a reference pseudo-noise sequence with a received pseudo-noise sequence modulated in a received spread spectrum signal.
U.S. Pat. No. 5,745,480 describes a multi-rate wireless communications system that supports a plurality of distributed user terminals in full-duplex simultaneous communications with a central base station, where each user terminal is provided on demand with one of multiple bit rates at a negotiated QOS.
U.S. Pat. No. 5,784,402 describes transmitter-receiver systems and circuits which employ binary and quadrature Feher""s modulation.
U.S. Pat. No. 5,802,467 describes an interactive microprocessor based wireless communication device that includes sound and data transceivers.
U.S. Pat. No. 5,805,017 describes a method of, and receiver for, receiving and demodulating M-ary FSK symbols, where M equals two or four, comprising over sampling a received signal to obtain sub-symbols which are treated as repeated DBPSK xcfx80/4 DQPSK symbols, respectively.
U.S. Pat. No. 5,818,127 describes an apparatus for electrical line communications using FM video modulation, and which includes FM video modulation circuits and an impedance matching coupler at each of two or more locations along a pair of line.
U.S. Pat. No. 5,825,810 describes a method for demodulating a received spread-spectrum signal that uses a minimum-shift-keyed (MSK) receiver.
U.S. Pat. No. 5,828,692 describes a cordless telephone system connectable to the public switched telephone network having a base station and one or more handsets communicating with the base station by an RF link utilizing a DBPSK I and Q demodulator with a digital AGC loop.
U.S. Pat. No. 5,828,707 describes a differential detecting apparatus that includes samplers, a differential detection calculating units, and two post-detection filters.
It is desirable to provide a system for communicating analog audio (voice) and/or digital data signals over the AC power lines. It is particularly desirable to provide such a system, and which makes use of differential binary phase shift keying (DBPSK) digital modulation techniques.
Accordingly, it is the primary object of this invention to provide a system for the communicating analog audio (voice) and/or digital data signals over the AC power lines, using a differential binary phase shift keying modulation technique.
Another object of this invention is to provide a system for the communication of analog audio (voice) and/or digital data signals that includes a DBPSK modulator and a DBPSK demodulator.
A further object of this invention is to provide a system for the communication of analog audio (voice) and/or digital data signals that lends itself to implementation in an ASIC because of its simplicity and digital modulation/demodulation techniques.
Another object of this invention is to provide a system for the communication of analog audio (voice) and/or digital data signals that minimizes the cost and complexity required of the modulation system.
Additional objects, advantages, and other novel features of this invention will be set forth in part in the description that follows and in part will become apparent to those skilled in the art upon examination of the following or may be learned with the practice of the invention. The objects and advantages of this invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims. Still other objects of the present invention will become readily apparent to those skilled in the art from the following description wherein there is shown and described the preferred embodiment of this invention, simply by way of illustration of one of the modes best suited to carry out this invention. As it will be realized, this invention is capable of other different embodiments, and its several details, and specific electronic circuits, are capable of modification in various aspects without departing from the invention. Accordingly, the drawings and descriptions should be regarded as illustrative in nature and not as restrictive.
To achieve the foregoing and other objectives, and in accordance with the purposes of the present invention, the DBPSK modulator is provided with a digitizer, a summer, a differential encoder, phase shifter and a transmitter. While the DBPSK demodulator is provided with receiver, a delay circuit, and a mixer.